Many modern jet aircraft, particularly military aircraft, include an augmentor section (popularly called an afterburner) in conjunction with their main propulsion gas turbine engine(s). Augmentors are used primarily to provide extra thrust for relatively short periods of time, which may be required during e.g., takeoff and high speed maneuvers. An augmentor consists basically of a cylindrical section behind the combustor chamber of a gas turbine, where fuel is injected, mixed with the turbine exhaust gases, and burned, so as to create a further expansion of the exhaust gases, increasing their velocity out the rear of the engine. This increase in velocity results, of course, in increased thrust.
When it is desired to commence augmentor operation in current augmentor designs, fuel is injected into the augmentor combustion chamber and ignition is initiated, generally by some type of spark discharge igniter. Since the rate of gas flow through an augmentor is normally much greater than the rate of flame propagation in the flowing gas, some means for stabilizing the flame must be provided, else the flame will simply blow out the rear of the engine, and new fuel being injected will not be ignited. The common means used for flame stabilization consists of placing some type of obstruction in the path of the gas flow to act as a flameholder. Such an obstruction, sometimes called a "bluff body", causes the flow of a portion of the burning gases to be recirculated in some region behind the obstruction. Generally several obstructions are used, spaced around the interior of the augmentor combustion chamber. In the regions where the gas flow is partially recirculated and the velocity is less than the rate of flame propagation, there will be a stable flame existing which can ignite new fuel as it passes. Unfortunately, obstructions in the gas stream inherently cause losses, and the efficiency of the engine thereby drops.
Accordingly, it is an object of the present invention to provide a flame stabilization means which does not involve slowing the gas flow with its attendant loss in efficiency.